The space
through which the Earth travels is largely empty, so there is not much for
the Earth to hit as it speeds along. But it is not totally empty; there
are scattered bits of dust and the occasional little rock, and when the
Earth collides with one the dust grain or small rock plows into the
atmosphere at a combined speed sometimes reaching hundreds of kilometers
per second.

At that
speed the friction of the object passing through the atmosphere is so
intense that the tiny object is instantly heated to many thousands of
degrees. The heat is so intense that the tiny grains of dust are
completely burned up in a fraction of a second, leaving only a momentary
bright streak and a bit of vaporized ash floating in the air. If it were
night and had you been looking in the sky at that moment you would have
seen what is sometimes called a "shooting star," the flash of a meteor
burning itself out in the upper atmosphere. On any given night under dark
skies you can see a dozen or more bright meteors, heavens reward for
having your eyes on the sky.

Bigger
swarms

But
sometimes the Earth encounters not just random bits of dust, but a more
concentrated swarm. In those cases many more than a dozen meteors will be
seen, and the rate at which meteors are seen may rise to 30, 50, even over
100 per hour. These are called meteor showers, and they are recurring
events that take place at the same time each year. Thus the Lyrids meteor
shower occurs in April 21-22 of each year, the Perseids on August 11-12,
the Leonids take place the night of Nov. 17-18 each year, the Geminids on
December 13-14, and so on.

(The names
"Lyrids," "Perseids," etc. refer to the constellation from which the
meteors appear to originate. The Lyrids appear to come from the
constellation Lyra, the Perseids from Perseus, etc. They donít really come
from the constellation, of course; its only an

optical illusion due to the combined
directions of travel of the meteors and the Earth.)

The reason
that the dates of meteor showers remain the same from year to year is that
on those dates the Earth reaches points in its orbit where there are known
concentrations of space dust and debris. These bits of dust and debris are
not stationary -- nothing in space is truly stationary -- but they are in
orbit about the Sun in a racetrack pattern, just as the Earth follows its
own "racetrack" around the Sun. But because the two "racetracks" cross
each other, each year when the Earth reaches the point where the orbits of
the Earth and the dust swarm cross each other, the Earth plows through the
thin trail of dust and for a few hours we see more meteors in the sky.

The
source of the swarms

What causes
these "racetrack" trails of dust is comets. Comets are clumps of dust and
ice a few miles across and they are very loosely held together. As they
travel in their orbits about the Sun they are continually scattering dust
and debris in their wake, and over time the path of their orbits become
one continuous trail of thin dust and debris. The orbits of most comets
donít cross the Earths orbit, but when one does then the Earth, in
subsequent years, will cross the dust trail of the comet and a meteor
shower will occur at that point each year.

Thus it is
that every meteor shower is believed to be associated with a comet. In
some cases the parent comet of a meteor shower can be clearly identified:
The Perseids appear to be associated with comet Swift-Tuttle, the Leonids
with comet Tempel-Tuttle, and both the Orionids and Eta Aquarids meteor
showers appear to be associated with Comet Halley (because the Earth
crosses Halleyís orbit in two places). In some cases the parent comet is
unknown and believed to be long extinct, but the dust trail remains to
mark its former orbit.

A near
miss

So what
would happen if the Earth did not cross the comets trail far back from the
comet, but rather very close behind the comet? In other words, what if we
crossed the comets orbit right after the comet had just passed? Obviously
we would be passing fairly close to the comet, and there would be more
comet dust and debris to encounter.

What
happens in those cases is that the meteor shower that would normally take
place becomes much more intense. The meteor rate may increase from one or
two a minute to tens or hundreds of meteors per minute, and there have
been instances when hundreds of meteors per second have been seen for
short periods of time.

Those very
rare cases where the rate reaches dozens or hundreds per minute are known
as "meteor storms," and the meteor storm that is credited with launching
the modern study of meteors occurred during the Leonids meteor shower on
the night of Nov. 12-13, 1833. Meteor storms had been observed before, and
just the year before the Leonids had put on a spectacular show, with one
observer in Boston counting over 8,000 meteors in only 15 minutes.

But what
occurred when the Leonids returned in 1833 was far beyond what anyone had
ever seen or even imagined possible. For several hours over the United
States there was a continual blaze of thousands and thousands of meteors
at a time. One estimate was that over 240,000 meteors fell during that
period, so many meteors in the sky at a time that many people were woken
from their beds and stared at the sky in panic, believing the sky to be on
fire. Many feared that it was the end of the world and dreaded what they
would see at daybreak.

At
daybreak, of course, everything was back to normal. Hollywood movies
notwithstanding, meteors typically vaporize in the atmosphere, a few drop
harmlessly to the ground, and there is only one known incident in history
when a meteor struck someone (and she only got a bruise from it). The only
living thing ever known to

have been killed by a meteor was a
very unlucky dog in Egypt many years ago. You are more likely to be struck
by lightning seven times in a row than to be hit by a meteor.

The show
returns

When the
Leonids returned in 1834 it was again a good meteor show, but nothing like
the sky-on-fire spectacle of 1833. The great meteor storm was back 33
years later in 1866. Astronomers predicted that the meteor storm would
return every 33 years, but it failed to materialize in 1899 or 1933.

Astronomers
began to think that perhaps the great meteor storms would not be repeated,
but right on time in 1966 the great meteor storm was back, particularly
over the western United States.

During a
peak period which lasted less than an hour there were hundreds of meteors
in the sky at once, and rates as high as 40 per second were observed.

Orbital
observations by then had pinpointed the source of the meteor storm as
Comet Tempel-Tuttle, which has a 33-year orbit. Those occasions when the
meteor storm occurred were linked with times when the Earth had passed
close behind the comet in its orbit. But the theory is not fully worked
out; though there clearly is a link with the comets position, there is no
good explanation why there was no meteor shower when we passed close to
the comet in 1899 and 1933.
. . .

óThis article describes the fulfillment of a great prophecy that is
repeated several times in Scripture by Joel, Jesus, and John the
Revelator. tcp